Data storage media are used to store and retrieve large amounts of digitally encoded data in a fast and efficient manner. Such media have been commercially provided in a number of different forms, such as magnetic, optical, solid-state (e.g., flash memory), etc.
Some media, such as magnetic and optical discs, can be rotated at a selected velocity while a head assembly transduces a read back signal to recover a data pattern stored to a media surface. The data patterns are often arranged on such media along a series of concentric tracks (e.g., discrete rings, a continuous spiral, etc.). An actuator, under the control of a closed loop servo circuit, can be used to position the head assembly adjacent the tracks in order to recover the data patterns.
Actuators can be rotary in nature so as to pivot about a pivot point adjacent an outermost diameter (OD) of a medium. In this way, the head assembly follows a curvilinear translation path across the radius of the medium. By contrast, linear actuators advance and retract the head assembly along a linear translation path across the radius of the medium.
In some cases, data patterns can be pre-written to a medium during manufacture to provide servo or other types of control information. The pre-written patterns may be written using an actuator with a different translation path geometry than that of a reader system used to subsequently access the medium. In such cases, the pre-written data may not conform to the finally utilized translation geometry of the reader system. This may lead to offsets (e.g., relative differences in angular position of the head assembly with respect to the data) as the head moves from one track to the next.